Process for rendering solid carbonaceous materials non-agglomerative



United States Patcnt O PROCESS FOR RENDERING SOLID CARBONA- CEOUSMATERIALS NON-AGGLOMERATIVE Application April 30, 1949, Serial No.90,636

2 Claims. (Cl. 202-16) This invention relates to a process for treatmentof a solid carbonaceous material. The process is particularly applicableto the treatment of those carbonaceous materials which tend toagglomerate on heating, e. g., caking coals; In one of its most specificaspects the present invention relates to a process for coating thesurface of a caking coal with powdered carbon to render the coalsubstantially non-caking in character.

The fluidized solids technique has been applied to processes for thedistillation and gasification of various solid carbonaceous materials.It is known, for example, that coal in finely divided form may betreated in a fluidized bed with hot gases to effect removal ofvolatilizable constituents therefrom by distillation. A number of solidcarbonaceous materials have been reacted with gaseous reactants in afluidized bed of particles of said material. Partial or completegasification of carbonaceous materials may be accomplished'by thismeans. Oxygen, hydrogen, carbon dioxide, and steam are useful gaseousreactants for the conversion of solid carbonaceous materials to valuablegases. Fluid bed gasiflcation is particularly adapted to the treatmentof coke or hard coal, such as anthracite, which does not tend toagglomerate on heating. Gasification of coal in moving beds, inprocesses such as the Lurgi process, is generally dependent for successupon a non-caking fuel. Frequently, however, those coals which are mostreadily available and most economical for gasification are bituminouscoals of the caking type.

The present invention provides an improved process by which caking coalsmay be pretreated to eliminate their caking tendency and eliminatedifficulties due to caking in subsequent carbonization and/ orgasification reactions.

Coal may be treated to prevent agglomeration by subjecting the coal todistillation to drive off at least a portion of the volatilizableconstituents or by partial preoxidation of the coal with anoxygen-containing gas. An expedient which has been proposed to preventagglomeration of caking coals involves admixing the raw coal with clay,ash, sand, or other inert material. A disad vantage of this procedure isthe necessity of using relatively large proportions of the inertmaterial, which is circulated through thegasification equipment with thecoal. Such inert materials reduce the capacity of the apparatus to aconsiderable extent because of the volume of inert material required foreffective results. From about 3 to about 10 parts of inert material mustbe used per part of fresh coal, depending upon the character of the rawcoal, to prevent agglomeration. A further disadvantage is found withsome coals in that the ash thereof tends to combine with the inertmaterial to yield a composite'substance of lower softening point thanthat of the ash, with a result that agglomeration is aggravated.

The process of the present invention avoids the ditficulties attendantupon these various methods of handling coal and provides a methodwhereby the coal may be effectively pretreated to avoid agglomerationand the resulting pretreated material charged directly to a subse-Patented Jan. 3, 1956 quent processing zone like a carbonization and/ orgasilication apparatus. The process of this invention may be carried outsimultaneously with the carbonization of coal by distillation toeliminate its caking tendencies and permit carbonization in a fluidizedor moving bed without resorting to the use of an added solid diluent.The carbon content of the resulting treated product is substantially ashigh as that of the original coal when the process is conducted underconditions which avoid the simultaneous carbonization or distillation ofthe solid fuel undergoing pretreatment.

In accordance with this invention, particles of a solid carbonaceousmaterial which has the property of caking or agglomerating when exposedto an elevated temperature are contacted at such an elevated temperaturewith a gaseous stream substantially non-oxidizing in character andcarrying in suspension finely divided carbon, such as soot, lamp-blackor carbon black, to effect the coating of the solid particles with thefinely divided carbon. The contacting of the particles of solidcarbonaceous material with the gaseous stream containing suspendedcarbon may be achieved by any of several conventional procedures. Forinstance, the solid particles may be passed through a rotary kiln whileflowing a hot gaseous stream containing suspended carboncountercurrently through the kiln. Alternatively, the solid particlesmay be dropped through a tower'against an ascending gaseous streamcarrying finely divided carbon.

In a preferred embodiment of this invention, a bed of particles of solidcarbonaceous material is maintained in a fluidized state in a treatingzone by the action of a stream of gas passing upwardly therethrough.Particles of fresh coal may be fed intermittently or continuously intothe fluidized bed and admixed with particles undergoing treatment.Finely divided carbon, for example, carbon black, lampblack, or soot, issupplied to the treating zone with the gas stream. Heat is supplied tothe treating zone sufficient to make the surface of the coal particlestacky and, if desired, to volatilize at least a porltion of thevolatilizable constituents therefrom. The particles of carbon black coatthe surface of the coal particles and aid in eliminating the cakingtendency of the particles. At the same time more or less of thevolatiliz-,

able constituents, particularly undesirable moisture in the coal, aredistilled from the coal. Treated particles of coal are intermittently orcontinuously withdrawn from the treating zone as'a non-caking product.Entrained particles of powdered carbon maybe separated from the eflluent gas from the treating zone and recycled to the fluidized bed;

The powdered carbon may be supplied from any suitable source, forexample, commercial carbon black or lamp-black may be admixed with thestream of treating gas Generally it' is preferable to generate thepowdered carbon by partial combustion of a hydrocarbon gas or oil and topass the resulting hot gaseous products of combust'i on and entrainedpowdered carbon into the treating zone. A number of processes for theproduction of carbon are knownin'the' art. Volatilizable constituentsdistilled from the coal may be used as a source of the pow dered carbon,for example, the hydrocarbon gases or oils may be recovered and.utilized for the production of powdered carbon.

Suitable non-oxidizing gases include hydrogen, carbon monoxide, steam,carbon dioxide, flue gas, natural gas,

and the like. Gases produced along with carbon black by partialcombustion of a hydrocarbon are generally suitableas a treating gasstream. These gases may serve to supply heatto the treating zone for thesoftening or ents from the coal and these may be recovered from thegaseous 'eflluent as hydrocarbon gases and oils.

An object of this invention is to provide an improved process for thetreatment of solid carbonaceous material.

Another object is tojprovide a process'for 'thetreatment of caking coalsand like solid fuels to render them substantially non-caking incharacter.

Still another object is to provide an improved process for thedistillation of volatilizable constituents from solid carbonaceousmaterials, such as coals and oil shale.

The drawing is a diagrammatic elevational view illustrating oneembodiment of the process of the present invention.

With reference to the drawing, coal is fed through line 1 into a feedhopper 2. An inert gas may be supplied through line 3 to build uppressure in the hopper. The gas also forms an inert blanket in the feedhopper, avoiding explosion hazards. The particles of coal from the feedhopper are fed through line 4 at a rate controlled by valve 5 into atreating zone 6. A fluidized bed of particles of coal undergoingtreatment is maintained within the treating zone.

The particles of coal undergoing treatment within the treating zone arefluidized by a gas passing upwardly therethrough. The fiuidizing gas,containing powdered carbon in suspension, is admitted to the lowerportion of the treating zone through line 7. Powdered carbon is producedby partial combustion of a hydrocarbon oil or gas in a carbon generator8. The hydrocarbon is supplied to the generator through line 10 while anoxygencontaining gas is supplied through line 9. Air or oxygen may besupplied to the generator as the oxygen-containing gas. The gaseousproducts of combustion from the generator, containing powdered carbon insuspension, are ideally suited as the gas for fluidization of the coalin the treating zone. The fiuidizing gas stream from the generator maybe supplemented by additional gas from any suitable source admitted toline 7 through line 12.

Heat may be supplied to the treating zone by any conventional means;preferably it is supplied by the gas stream entering through line 7.Alternatively, the heat may be supplied by indirect heat transferthrough the walls of the treating zone or by heating elements or coilsdisposed in the fluidized bed.

Particles of fresh coal admitted to the treating zone are admixed withparticles of coal undergoing treatment therein. The fluidized bedcomprises largely particles which have received suflicient treatmentwith hot gases containing powdered carbon to render them non-caking andfree-flowing under the treating conditions. The fresh particles of feedare dispersed in the treated parti tiles and subjected to heating to atemperature sufficient to soften or tackify the surfaces of theparticles and permit coating them with powered carbon. The fluidized bedeffects rapid mixing of the fresh coal and treated particles and rapidheating of the feed particles to the treating temperature. Dispersion ofthe feed particles in the treated particles prevents contact between thefresh particles until they have received suflicient treatment to renderthem non-agglomerating. Preferably the temperature of treatment issufficient to volatilize at least a portion of the volatilizableconstituents, especially moisture, from the coal.

The particles of treated coal are withdrawn from the treating zonethrough line 13. The treated coal particles are discharged into aconveyer 14 through which they may be passed to storage or to subsequentoperations.

The fiuidizing gas after passing through the treating zone is dischargedthrough line 16 into a separator 17 of the cyclone type for removal ofentrained particles therefrom. Solid particles separated from the gasstream in the separator 17 are returned through line 18 to line 7 intoadmixture with the fiuidizing gas and thence to the treating zone. Thegas, substantially free from solid particles, is discharged through line'19. This gas may be processed for the separation of condensable oilsresulting from the distillation of the coal and may be recycled to thetreating step, used in carbon generator 8 or utilized as a fuel gas orthe like.

The temperature in the treating zone should be high enough for theparticular solid fuel undergoing treatment to ensure that the soot orpowdered carbon will stick to the surfaces of solid fuel particles.Generally, a satis factory temperature will be at least about 600 F. andpreferably at least about 750 F. With most-solid fuels like coal,temperatures in excess of about 1000 F. will cause appreciablecarbonization of the coal, i. e., an appreciable quantity ofvolatilizable constituents will be distilled from the coal. The pressuremay vary from about atmospheric to about 500 pounds per square inchgauge and is determined largely by subsequent process requirements, thepressure having no appreciable eflect upon the efficiency of the presentprocess. Thus the pressure may be determined by the desired pressure atwhich the eflluent gas or treated coal are supplied to associatedprocesses. For example, in the gasification of coal it is oftendesirable to operate the gasification reactor at a pressure within therange of from about 50 to 500 pounds per square inch gauge. The treatingstep of the present invention may be operated at a comparable pressureso that the treated coal may be supplied directly to the gasificationzone without any difliculties due to the pressure at which thegasification zone is operated. It is wellto observe that the pretreatingprocess of this invention can serve the dual function of renderingcaking solid fuels non-agglomerating and simultaneously preheating themprior to charging them into a gasification zone or other processing zonemaintained at an elevated temperature.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and, therefore, only such limitations should beimposed as are indicated in the appended claims.

I claim:

1. The process of rendering fresh particles of caking coal non-cakingwithout substantial carbonization, said particles being of a sizeadapted for gasification in a settled moving bed, which comprisesintroducing said fresh particles into a dense phase fluidized massmaintained at an elevated temperature of at least 600 F. adapted tocause tackiness of the surfaces of said fresh particles while passing asubstantially non-oxidizing gas containing finely powdered sootsuspended therein upwardly through said mass to effect the fluidizationthereof and to coat the tacky surfaces of said fresh particles with saidsoot, said fluidized mass at all times consisting essentially of coalparticles which have been thus rendered substantially non-caking, andwithdrawing coal particles from said mass prior to substantialcarbonization as substantially non-caking coal particles coated withsoot.

2. The process of claim 1, wherein the non-oxidizing gas containingfinely powdered soot suspended thereinis generated by the partialcombustion at elevated temperature of a fluid hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS2,396,036 Blanding Mar. 5, 1946 2,414,586 Egloff Jan. 21, 1947 2,471,119Peck et al May 24, 1949 2,512,076 Singh June 20, 1950 2,534,728 Nelsonet al Dec. 19, 1950 FOREIGN PATENTS 394,747 Great Britain July 6, 1933621,512 Great Britain Apr. 11, 1949 104,346 Australia June '22, 1938

1. THE PROCESS OF RENDERING FRESH PARTICLES OF CAKING COAL NON-CAKINGWITHOUT SUBSTANTIAL CARBONIZATION, SAID PARTICLES BEING OF A SIZEADAPTED FOR GASIFICATION IN A SETTLED MOVING BED, WHICH COMPRISESINTRODUCING SAID FRESH PARTICLES INTO A DENSE PHASE FLUIDIZED MASSMAINTAINED AT AN ELEVATED TEMPERATURE OF AT LEAST 600* F. ADAPTED TOCAUSE TACKINESS OF THE SURFACES OF SAID FRESH PARTICLES WHILE PASSING ASUBSTANTIALLY NON-OXIDIZING GAS CONTAINING FINELY POWDERED SOOTSUSPENDED THEREIN UPWARDLY THROUGH SAID MASS TO EFFECT THE FLUIDIZATIONTHEREOF AND TO COAT THE TACKY SURFACES OF SAID FRESH PARTICLES WITH SAIDSOOT, SAID FLUIDIZED MASS AT ALL TIMES CONSISTING ESSENTIALLY OF COALPARTICLES WHICH HAVE BEEN THUS RENDERED SUBSTANTIALLY NON-CAKING, ANDWITHDRAWING COAL PARTICLES FROM SAID MASS PRIOR TO SUBSTANTIALCARBONIZATION AS SUBSTANTIALLY NON-CAKING COAL PARTICLES COAT WITH SOOT.